Today's spit take: Willis isn't the largest tenant in the Willis Tower? What?

Willis Tower, formerly known as the Sears Tower, turns 45 in May 2018. The 110-story tower, once the tallest building in the Western Hemisphere, has seen many changes in residents over the years, and in 2009 a new glass ledge was introduced on the building's 103rd floor.

Eric Zorn

Melissa Harris' story today --Willis Tower for sale, has likely buyer -- tells me somthing I didn't know about the landmark structure formerly known as the Sears Tower:

The building — co-owned by real estate mogul Joseph Chetrit, developer Joseph Moinian and Skokie-based American Landmark Properties — is currently 84 percent leased. It is home to United Airlines’ global headquarters and the headquarters of the law firm Schiff Hardin LLP. The two companies are the tower’s largest and second-largest tenants, respectively.

So why isn't it the United Tower or Schiff Hardin Tower? Because of an agreement in 2009 --

-- in which London-based insurance broker Willis Group Holdings agreed to lease a portion of the building and got naming rights at the same time.

I didn't fuss much about the name change because I was under the impression what Willis was the main or at least biggest tenant in the building. It doesn't sit right with me, however, that naming rights should be sold to a lesser tenant, as it violates a certain expectation and understanding.